I've always got my repairs done at Binks Sail Loft in Somerton Park (just south of Glenelg). The blokes there have plenty of experience and do a good job, but you gotta be patient. My last was a few seasons back now and I can't recall how much it cost, but I think it was quite reasonable.
binksmarine.com.au/services/binks-sail-loft/the-sail-loftPS: to find old SB posts google your terms and add site:seabreeze.com.au to the end, for example:
sail repairs adelaide site:seabreeze.com.au